2026 Drama: Alleged engine loophole

[SealTheRealDeal]

How hard would it be to ensure that the expanding component(s) maintain optimal chamber geometry? I know all engines need to factor that in to some extent, but I also assume that this trick involves more than the typical/expected amount of thermal expansion given teams are complaining.

[dialtone]

How hard would it be to ensure that the expanding component(s) maintain optimal chamber geometry? I know all engines need to factor that in to some extent, but I also assume that this trick involves more than the typical/expected amount of thermal expansion given teams are complaining.

This is not thermal expansion. The alloys are determined by the rules.

[Tommy Cookers]

Materials that can be used:
15.8.3 Connecting rods: “Connecting rods shall be manufactured from iron or titanium-based alloys and shall be machined from a single piece of material without welded or joined assemblies…”
15.8.4 Crankshaft: “Crankshafts shall be manufactured from an iron-based alloy.”

how are these rules ?
eg what constitutes iron-based - and what doesn't ?
what constitutes titanium-based - and what doesn't ?

can the FIA even write a sentence in English ?
eg is it 'iron or titanium-based alloys' ? or is it 'iron-based alloys or titanium-based alloys' ?

[sucof]

Sorry if this is noob but:
If the thermal expansion is like most people here suggested, then that shall reduce the volume of the cylinders...?
If materials expand on the piston head surface for example because of the engine got up to its operating temp, then it stays there... So how would that even improve compression ratio, when the starting volume is already smaller?

Or, you all suggest that the expanding alloy expands and contracts in every cycle??

- My idea would be that the expanding alloy is not within the cylinder, but on the crankshaft.
And the expansion is lengthening the travel of the piston, while the "down" position is unchanged.


Additionally, I mentioned this before: To my knowledge F1 engines can not be even rotated when cold, then how they are measuring compression?

[SealTheRealDeal]

Possibly a very dumb question, my apologies if it is: Could it be fuel related? The regulations have switched from mass-based fuel flow to energy-based fuel flow, and iirc there were whispers earlier that Petronas' 2026 fuel was down on energy density. Could having a higher volume/mass of lower energy density fuel in the chamber simulate higher compression? I doubt that any hp gains would make up for the weight penalty of carrying more fuel...

[dialtone]

This whole thing doesn’t make much sense to me either. F1 engines are usually around 80-100C to be turned on without seizing.

Thermal expansion just doesn’t fit this, and the ambient temperature measure (as in engine off and around 20-30C) would mean just blueprint because you can’t physically move the piston with its tolerance without lubricants flowing.

Crankshaft expanding would reduce the minimum volume but also reduce the maximum expansion.

The only expansion that would be plausible is horizontal, but even there I’m skeptical. This really has to be geometry or connected volumes in what would be considered the cylinder volume.

[Badger]

Possibly a very dumb question, my apologies if it is: Could it be fuel related? The regulations have switched from mass-based fuel flow to energy-based fuel flow, and iirc there were whispers earlier that Petronas' 2026 fuel was down on energy density. Could having a higher volume/mass of lower energy density fuel in the chamber simulate higher compression? I doubt that any hp gains would make up for the weight penalty of carrying more fuel...

Not sure if higher compression of a lower energy density fuel would yield any relative gain. Intuitively it seems like it wouldn't, the compression per unit of energy would remain similar.

[vorticism]

Possibly a very dumb question, my apologies if it is: Could it be fuel related? The regulations have switched from mass-based fuel flow to energy-based fuel flow, and iirc there were whispers earlier that Petronas' 2026 fuel was down on energy density. Could having a higher volume/mass of lower energy density fuel in the chamber simulate higher compression? I doubt that any hp gains would make up for the weight penalty of carrying more fuel...

Good question. Much different orders of magnitude. The combustion chamber volume compared to the rumored thermal expansion volume is around 10:1 while the air:fuel volumetric ratio near stochiometric mixtures is around 10,000:1 uncompressed. Compressed that ratio may be around 500:1 i.e. the fuel occupies around 1/500th of the combustion chamber at TDC but you need to reduce the combustion chamber by roughly 1/10th in volume in order to match the preceding discussion. A 5mm ball bearing inside of a shot glass. Say the fuel is 10% more voluminous per energy unit. Replace your petrol with butanol. How much will the meniscus raise if the 5mm ball bearing is replaced with a 5.5mm ball bearing--not by 10%, although it would raise slightly. That said I don't think alteration of the geometric compression ratio is the trick at play here.

[SealTheRealDeal]

Possibly a very dumb question, my apologies if it is: Could it be fuel related? The regulations have switched from mass-based fuel flow to energy-based fuel flow, and iirc there were whispers earlier that Petronas' 2026 fuel was down on energy density. Could having a higher volume/mass of lower energy density fuel in the chamber simulate higher compression? I doubt that any hp gains would make up for the weight penalty of carrying more fuel...

Good question. Much different orders of magnitude. The combustion chamber volume compared to the rumored thermal expansion volume is around 10:1 while the air:fuel volumetric ratio near stochiometric mixtures is around 10,000:1 uncompressed.

I see, thank you.

[TimW]

How hard would it be to ensure that the expanding component(s) maintain optimal chamber geometry? I know all engines need to factor that in to some extent, but I also assume that this trick involves more than the typical/expected amount of thermal expansion given teams are complaining.

This is not thermal expansion. The alloys are determined by the rules.

You could play with the temperature differences too, at least in theory. E.g. heating up the crankshaft would increase compression ratio.

[TeamKoolGreen]

What if the piston/chamber was designed in such a way, that volumetrically based on static measurements it is 16:1 ratio, but in reality it runs on 18:1 "effective" volume, I guess achieved by some slot and "dead" volume beneath, could also be, that heat expansion just "closes" the slot and by this way exclude the additional volume surplus needed for achieving 18:1. My 5 cents, fueled by post from vorticism and his thoughts on clever geometries.

If they are really getting 18: 1 from a static 16:1 then the engine has some kind of moving parts that involves a pre chamber or something. There's no way they are getting 18:1 just from some thermal expansion of a conventional design.

[AR3-GP]

This whole thing doesn’t make much sense to me either. F1 engines are usually around 80-100C to be turned on without seizing.

myth.

[TEHNOS]

This really has to be geometry or connected volumes in what would be considered the cylinder volume.

My thoughts in this direction too. Bigger theoretical volume, smaler functional.

And some import from another forum:

Wouldn’t an additional combustion chamber create a lower compression ratio?

Exactly. So if that additional "combustion chamber" were to be accessible at ambient temperature and closed off at operating temperature (due to thermal expansion), then that could be another way for the engine to exhibit different compression ratios at different temperatures.

Is it? When the additional chamber is in use, it should have its use, it cannot be sealed off?

Unless this second chamber has a functional reason like injection and improving the efficiency, it may decrease the performance. 18:1 is like a diesel ICU, which needs speccial attention to achieve optimal combustion, I believe, for which this second chamber must remain functional, meaning it cannot be sealed off at operational temperature? (about 800 degrees?)

But, yes, the second combustion chamber in a certain shape could shrink more than the main combustion chamber, perhaps?

Because the main combustion chamber has cylinder sleeves that are designed to become slightly larger to accommodate the movements of the piston. When the cylinder block shrinks in length, accommodated by carbon steel at 800 degrees, the sleeves are to shrink together in length, which is an issue because the same sleeves expand in diameter to allow piston movements!

But the second combustion chamber has no sleeves or any moving parts, so when it can shrink, it shrinks more.
The second combustion chamber is surrounded by metal that expands when it’s hot, which shrinks the cavity of the second combustion chamber. if the second combustion chamber is a triangle shape in the cross section, then it becomes like a star shape cross section, let’s say.

https://forums.autosport.com/topic/2292 ... ry11084432

[Rodak]

Additionally, I mentioned this before: To my knowledge F1 engines can not be even rotated when cold, then how they are measuring compression?

It must be pretty hard to assemble them..... And they're not measuring 'compression' they're measuring geometric compression ratio.

[SealTheRealDeal]

This really has to be geometry or connected volumes in what would be considered the cylinder volume.

My thoughts in this direction too. Bigger theoretical volume, smaler functional.

And some import from another forum:

Wouldn’t an additional combustion chamber create a lower compression ratio?

Exactly. So if that additional "combustion chamber" were to be accessible at ambient temperature and closed off at operating temperature (due to thermal expansion), then that could be another way for the engine to exhibit different compression ratios at different temperatures.

Is it? When the additional chamber is in use, it should have its use, it cannot be sealed off?

Unless this second chamber has a functional reason like injection and improving the efficiency, it may decrease the performance. 18:1 is like a diesel ICU, which needs speccial attention to achieve optimal combustion, I believe, for which this second chamber must remain functional, meaning it cannot be sealed off at operational temperature? (about 800 degrees?)

But, yes, the second combustion chamber in a certain shape could shrink more than the main combustion chamber, perhaps?

Because the main combustion chamber has cylinder sleeves that are designed to become slightly larger to accommodate the movements of the piston. When the cylinder block shrinks in length, accommodated by carbon steel at 800 degrees, the sleeves are to shrink together in length, which is an issue because the same sleeves expand in diameter to allow piston movements!

But the second combustion chamber has no sleeves or any moving parts, so when it can shrink, it shrinks more.
The second combustion chamber is surrounded by metal that expands when it’s hot, which shrinks the cavity of the second combustion chamber. if the second combustion chamber is a triangle shape in the cross section, then it becomes like a star shape cross section, let’s say.

https://forums.autosport.com/topic/2292 ... ry11084432

So at operating temperature the engine displacement would be less than 1.6L by a non-negligible amount?